Variable-speed electric motor.



No. 8427,088. l PATENTED MAR. 12, 1907. I. G. LINCOLN. VARIABLE SPEEDELECTRICl MOTOR.

` A??LIOATION FILED JAN. 12.1906. v

l JOHN C.

A iieldstructure of the motor, whereby variawell in eitherying-tiel'd'.during the high-speed positions-of brushes of the motor,and particularly at the armaturein association with a rocker- UNTTEDsTATEsy PATENT OEETCE.

LINCOLN, OE EAsT CLEVELAND,

COMPANY, OF CLEVELAND, OHIO, A CORPORATION OF OHIO.

VARlABLEp-SPEED ELECTRIC IVIOTCPR.

No. 847,0 8especification of Letters Patent. y Patented March 12, 1907.

Application filed January 12, 1906. Serial No. 295,765.

To all" 11j/12,0771, t may concern:

Beit known that I, JOHN C. LINCOLN, a citizen of the United States ofAmerica, and a resident Of East Cleveland, in the County of Cuyahoga andState of Ohio, have invented certain new and useful Improvements in Va-Ariable-Speed Electric Motors, of which the following is a specification,reference vbeing had to the accompanying drawings, forming a partthereof. p

VMy invention relatesjto'improvements in variable-speed electric motors,being prefer-y ably applied to that type of motor having field andarmature windings associated in shunt relation and provided withsuitable means for securing the .lateral or axial movement of thearmature with respect to the takes the form of a three-pole magnet,carrying the main'eXciting-coil upon an inner pole or leg thereof, whiletwo ...coils oppositely wound are mounted. upon the exterior poles andserve to prevent the usual drop in speed under heavyloads. C

Further details of my invention and the structural features and'operation of my improved motor will be iliade clear by referring to theaccompanying sheet of drawings, wherein Figure I is an end elevation ofan electric motor constructed in accordance with my invention. Fig. IIis a side view of said motor, partially'broken away and insection. Fig.IIIv` is a detail view of the preferred magnet structure withwhich isassociated an eX- planatory tional view structure. Fig. V shows amodified type of electromagnet for obtaining thecommutatingfield.4 Fig.VI is a detail showing the referred means for" securing the axialadjustment of thearmature, and Fig. VII .dia-

grammatically shows the features. of 'the shunt-wound motor, thecommutating-magnet Structure, and 'areversing-switch forthe 'motor.

- Throughout the several figures ofthe drawtion in speed is attained.

The object of my invention has been to so construct electric motors asto secure anunusual range in the speed variation thereof, meanwhileavoiding harmful sparking at the high speeds.

The said improvements in addition adapt themotor for operating equallydirection of rotation of the ar-` mature and admitofrcloselyrcontrolling the magnetic'iieldfor preventing sparking, whichI have herein termed the commutatingfield. i' v Referring brieiiytothe-illustrated motor embodying my invention I; maynsay that it consistsof the usual field structure, within which the motor-is designednormally to rotate. Associated with said Yarmature are means lforwithdrawing it laterallyfrom the field structure, said means comprisingscrew mechanism and a spring opposing the pull of reference to indicatesimilar parts.

Within the iron casting e are shown the ing t eir exciting-coils c. yarmature d, wound in shunt relation ther'with, prefer- -ably isfrusto-conical in shape, as is the; armature-s ace formed by the severalpolepieces oy the field structure, although the more commonly-usedtypesof armature and field structure maybe used inV arm or lever actingupon the en d of the arma, ture-shaft to Withdraw the armature from itsnormal position of rotation.- The most important feature of myinvention, however, resides in the means for affording a commutattoslide longitudinally inits bearing f at one side of the motor, while theother bearing g is carried by means of a spider or lframe h, slidingwithin Ways fi, rovided atthe other side of the motor. Ain enlarged cais formed upon the bearing g, with whic roll ers k, attachedto therocker-arm or lever l, 'are adapted to engage, n said lever is pivotallysecured a short distance 'from the 'fulcrum of the lever to a tapped artor clevis m,whe1'eon a stiff p spring n adjustment for the armature.,`comprising .an electromagnet lateraiv positioned beyond the fieldstructure of the motor adjacent to the armature when withdrawn'therefrmtoits highspeed ositions, this electromagnet being connecte in serieswith the armature of the motor. Preferably this electromagnet ings,Ihave employed the same character fv racticmg my invention. Thearmature-sha t e is mounted OHIO, ASSIGNOR TO TIPIE LINCOLN diagram.Fig. IV is a'central sectlfnoughl the preferred magnet four oles b of alshunt-wound motor, carryy The other end ofis. mounted to oppose thenormal in- Y Cooperating or cievis is a threaded Ween two oi: the field--rii'nating in a hand-wheel p. es the preferred means lor ei"- Aialwitliiilraw'al of the armature s normal position within the 'l'ield`'-ueture in order to increase the speed ot ro- By merely turning thehand-wheel in the direction to inwardly draw the upper end oit therocker-arm or lever itis apparent that fie armature must be axiallymoved toward the left, II, out ot its normal or i: -speed posi tion orrotation within the Lield i structure. Upon the resulting increase ofspeed, however, particularly under heavy loads, it has been found thatvery serious sparking at the brushes results in this type of motor, andI have sought to provide means .2o whereby all sparking will be avoidedand at the same. time overcome the utendency of the armature to slowdown or fall away in speed under full load. T ese results I haveaccomplished by providing a separate laterally-positioned magneticsystem or systems found 'in the magnets g, disposed at either side ofA lthe motor between two of the field-poles. The windings 7 thereof areconnected miseries i Tith the armature, as shown in Fig. VII,

3o and by this arrangement in consequence I am enabled to operate themotoi equally well in either direction of rotation, since the reversalof current through the armature necessarily reyerses the polarity of themagnets 3 5 gf rihe corinnutating field-poles of these magnets, it willbe understood, are positioned opposite to those coils of thearmaturewhich aie undergoing commutation, the armature being in any of itspositions of withdrawal. These coils, accordingly, are magneticallyinfluenced for this brief period in a manner to oppose the currentpreviously lowing through said coils, and thus avoid sparking during theoperation of the armature in its highe speed positions.

A modified type of electromagnet for providing a con'iniutating-field isshown in F ig. IJ, wherein' the windings i" are disposed upon an ironcore s, 'formed with lateral extensions t to subtend thequadrant ci: acircle and lie between but beyond the adjacent poles of the iieldstructure. The coils oi the armature when axially drawn beneath theextensions t -will be subjected to their magnetism at the moment ofcommutation and sparking will beavoided7 it being understood that two.of

the modified type of magnets are used. Ii

one alone is employed upon the motor, the

flux theie'hrom must be twice as strong as beeo fore', and the armatureof series-conne`cted type would then preferably be provided with twobrushes only. I will'rexplain this and other teatri" of operation morein detail, however, by ma hng reference to the pre- 6 5 eri'edelectromagnet structure for' embodysenese ing my invention disclosed inthe other igures oi the. drawings and particularly in Figs. III and IV.t

In the structure of Fig. III E-sliapecllaminated plates are suitablyriveted together to form a magnet q, having three limbs. A la'ti eralextension o preferably' is provided for carrying the magnetic lines overa greater area than is covered by the laminated plates. Upon these polesthe winding fr is disposed, before; but in order to provide against thenormal speed drop said coil r is subdivided, the central limb ot themagnet carrying the main portion thereof, (designated as winding 11.1,)which servos to supply the commutatingdiold for the motor, whilewindings and y, respectively, wound to excite similar and oppositepolarity in their cores, will genera-te the ield o t 'force serving tocounterat. the speed drop. Obviously these functions are entirelyseparate, and either set oic windings may be employed independently toef'- iect their particular functions in the im-Y proved motor.

In the diagram of Fig. III, I have designated the polarity of theseveral parts of the main and secondary magnetic systems by thecharacters ii and S', and it is to be assumed that the armature in Fig.III is rotating in a contra-clockwise direction.

With the structural features in mind the mode of operation will now bereadily appreciated. In order to increase the speed of the armature, theiields being under the influence of a given constant current, it isnecessary only to axially withdraw the armature Jfrom the fieldstructure, thus increasing the reluctance of the air-gap between thearmature and field, andconsequently decreasing the magnetic fluxentering the armature from the main field structure.

Since the counter electromotive force of an armature is proportional tothe product of the speed and the magnetic ux and such product ispractically constant for a given iro primary electromotive force, suchdecrease in the magnetic flux must be accompanied by an increase inspeed, which necessarily takes place. The withdrawal of vthe armaturefrom the magnetic field reduces the area of the airgap, and thusveffects an increase' in the reluctance thereof. This is true whether 'ornot the interior armature-receiving space and coacting armature be 'or'.ordinary cylindrical form; but by employing the truste-conicalconstruction for the armature and fields, as

ICO

.(lescribed, not only is the area of the air ap v senese ltromotiveforce in opposition to the current previously flowing therein, the onereversing the other .to prevent sparking,

In Fig. III, N represents one 4of the main i i elds and is assumed to bea north pole, and

. in consequence-S. will be an adjacent' main Y' limb of thereturn-circuit.

' between the poles of being southpole. f

' The commutating-pole z ofthe electromagnet is excited bythe coil w.The flux from the'mainpoles N andgS is exactly the same as the flux inany ordinary four-'pole motor. The flux from the commutating-pole znormally divides. The two lines 1 1 indicate the normal division anddirection of the flux from the commutating-pole. Half of it will flow toone limb of the return-circuit on the righthand side of the centercommutatingole, and the other half will iiow to the left-fiand It isclear that the flux Z l from the commutating-pole z to thereturn-circuit is opposed by the magneto-motive force of the armature.The' amount of this opposition will be proportional to the number ofarmature-conductors inclosed by the flux from the 'main pole z or,referring to the diagram, to the number of armature-conductors embracedwithin the. lines v1 -1 and the circumference of the armature d.

It isclear that. the strength of the'main ole z willbe proportional tothe current flowmg through the coil w, and the commutati'ngA action.thereof .will be proportional to the amount of current to be commutated,since said coil is in series relation to the coils ofthe armature.

The function of the coils w and 'y is entirely independent of thefunctionl of the. coil w. Coils and y are provided only for thepurpose-of regulating the sp'eed or of preventing the ordinary speed drowhich occurs 4'as-the motor is brought to fu l load.

It is clear that the speed is inversely propn'tional-to the flux fromthe vmain poles N and S. Anything which decreases this net fiux raisesthe speed.; Conversely, 'anything that increases. the net flux reducesthe speed. The two poles excited, respectively, by coils and ly producean auxiliary fiux represented by the 1ine`2in op osition to the mainflux and S. The amount of thisflux is proportional to the currenttraveling through the coils and ly, and by providing the proper numberof turns on the" coils the speed `can be perfectly controlled. Ifrequired, the speed can be made higherat full-load than at no load.Actually, instead two separate and distinct fluxes, 'as indicated in thediagram,.-t he main flux from .those slrilled in the art.

the pole z instead of dividing equally, as it would norma ly tend to do,returns unequal'y y more of the ur returning through the rightl handpole than returns through the other pole. It is clear that the result asfar as the speed drop is concerned will be the -same whichever method offlux distribution is assumed.

VFrom a consideration of the foregoing it will he4 appreciated that thesecondary magnetic system or systems in motors of this type may compriseone or more ofthe electromagnets herein set forth and that the windings1" may be disposed either to provide thecommutating-field referred to orto serve as a 'speedfdrop be accomplished thereby with the preferredtype of electromagnet, since it is obvious that the windings may beomitted either l from the outer or inner limbs of said magnet.

.Preferably twov of such magnets oppositely or diametrically positionedare employed in' a four-pole motor, although one alone or more magnetsmayv be used with proper proportioning of the windings.

' The active portion of the winding r, asthe winding w, Fig. III, shouldbe supplied with sufficient turns so that at any load the flux from thepole into the armature issuflicient to produce sparkless commutation,which result is materially augmented by the series connection of thewinding with the armature. The proportioning of the coils, however, maybe, mathematically calculated by It maybe observed as a generalstatement that4 the windings w will usually haveV approximately tentimes the number' of turns that are provided for windings and y.

By reason of the structural features presented by the preferred type ofelectromagnet, having the three limbs for affording read. ily-elosedpaths for lthe lines of magnetic force generated by the cmmutating-polez, said magnet is better adapted for the purpose herein set forth thanany other form with which I am acquainted, although I do not desireftobe understood as necessarily restrict ing my invention to the precisestructural features above specified and shownv in the drawings.,

by those .skilled in lthe art, as

bination withits field structure, of a laterallypositioned magneticsystemv beyond the fields, means for exciting the same, 'compris-` ingwindings thereon in series circuit with the armature of the motor, anarmature mounted normally to rotate beneath the fields, and suitablemechanism for effecting the relative lateral movement of the armatureand field structure, adapted to increase the speed of rotation and-simultaneously subject the armature to the excited magnetic system,substantially as set forth.

2. In a variable-speed electric motor, the

corrective, or both functions may too and accordingly I claim said in- 4ventiorn together with such modifications as vthe field structure,comprising a magnetic core positioned beyond the field structure closelyadjacent to the armature when withdrawn therefrom, and exciting-windings upon said core adapted to produce a magnetic field for thearmature-coils at the moment of commutation, substantially as set forth,

3, In a variable-speed electric motor of the general class described,the combination with i its field structure, of an armaturemountedelectromagnets normally to rotate therein, means for effectingthe partial axial withdrawalof the armature from its eld structure toincrease its speed of rotation, and a separate magnetic system laterallypositioned to subject the armature- .coils to a field at the moment ofcommutation; 'said magnetic system being-excited by windings in seriesrelation with the armature, substantially asset forth.

Il. ln a vari able-speed electric motor of the general class described,the-combination with its field structure, of an armature mountednormally to rotate therein, means for eecting the partial axialwithdrawal of 'the-arma.- tu're from its field structure to increase itsspeed of rotatioruand a separate magnetic system suitably excited tosubject thecoils of the armature to lines of magnetic force inopposition to those generated by the field structure, whereby the normalspeed drop of the motor is corrected, substantially as set forth.

5. ln a variable-speed electric motor ofthe general class described, thecombination with its field structure, of an armature mounted normally torotate therein, means for effecting the partial axial withdrawal of thearma: ture 'from its field structure to increase its speed oi' rotation,and separate Amagnetic systems laterally positioned beyond the fieldstructure comprising a pole piece or coresuitably excited topresent apolarity similar to that of the rearwardly and laterally adjacent poleof the eld structure and a second pole piece or core suitably excitedtosub'ject the armature-coils to lines of force in opposition to thosegenerated by the field structure, whereby a commutating-field isproduced and the speed 'drop is" corrected, respectively, substantiallyas set forth. n

6. ln a variable-speed electric mctoecthe class described, thecombination with. its eld structure, of twolatgmllyepositionedhaving'i'egeit -windings thereon in series relation with the armature;

Athe same affording commutating-fields, an

armature normally rotating within the field canoas structure, and meansfor partially withdrawing the armature from said field structure intopositions of adjustment beneath the comrnutating-fields, substantiallyals set forth.

7. In a variable-speed electric motor of the class described, thecombination with its field structure, of laterally-positionedelectromagnets having a plurality Vof windings upon the respective limbsthereof in series relation with the armature; said windings beingadapted respectively to supply a commutating-field and to subject thecoils of the -armature to lines of magnetic force in opposition to thosegeneratedv by the field structure, an armature normally rotating Withinthe field structure, and suitable mechanism for partially withdrawingthe amature from said field structure into positions ,of adjustmentbeneath the electromagnets, substantially asset forth.

ln a yariable-speedelectric motor of the class described, 'thecombination with its field structure, of an armature mounted normally torotate therein, means for effectingy the partial withdrawal of thearmature'axially from said field structure," and a heavy springassociated therewith adapted to counterbalance the inward pull of thearmature during the period of its withdrawal, substantially as setforth.

9 In a variable-speed electric motor vof the class described, thecombination with its field structure, of an armature mounted normally torotate therein, and means for ef- ICO fecting the partial 4aria-lwithdrawal of the armature from said field structure, com ,rising arocker-arm or lever, and screw m'ec 1anism associated therewith adaptedto actuate said rocker-arm or lever and withdraw the armature from thefield structure to effect an increase in speed, substantially as setforth.

10. In a variable-speed electric motor of the type herein set forth, thecombination with its field structure, of an armature mounted normally torotate therein, a rockerarm or lever connected thereW/it -,a springopposing the movement of. thegf c'kerarm and armature, and screwmechanism associated therewith .for actuatingv the rocker-4 armpartially to withdraw the-'armature axially from its normal position ofrotation within the field, strpcture, substantially as set forth.

11. In a variable-speed electric motor of the t e herein set forth, thecombination With its field structure, of an armature mounted normall torotate therein, a slidiig bearing for t e armature, a'supporting frameor spider for said bearing, a rocker-arm er iever associated qtherewith,a spring opposing the movement of saidrocker-arm, and crew mechanism 'positioned within the motor-frame adapted to actuate the recher-arm andthe armature-bearing, whereby said im los lilo

mature is axially vWithdrawn from its normalposition of rotation Withinthe Jfield structure,

substantially as set forth.

the type herein set forth, withk its field structure,

mounted normally to the combination of an armature rotate therein, meansfor effecting the partial Withdrawal of the armature axially from saidield structure, cornprising a connecting rocker-arm or lever, acounterhalancing-spring, and screw mechanism associated therewith formoving the armature, and additional means for treating a commutatingmagnetic eld for the armature 'in its positions of Withdrawal,substantially as set forth Signed at Cleveland, this 9th day of Jannary, A. D. 1906, in the presence of the undersigned Witnesses.

JOHN C. lLNCOLN` Witnesses:

FRANK H. FORREST, ALBERT LYON LAWRENCE.

